Phytoplankton Density Research Articles

Remotely sensed-based analysis about climatic and landscape change effects on phytoplankton bloom in Barra Bonita Reservoir (São Paulo State, Brazil)

The constant land use and land cover (LULC) changes combined with climatic factors are frequently assigned to anthropogenic eutrophication, one of the main ecological imbalances in aquatic systems characterized by dense phytoplankton proliferation. Beyond the degradation of freshwater ecosystems, some cyanobacterial and algae species produce toxins harmful to living beings. Distinct studies in the literature, usually supported by in situ data, have discussed the influence of LULC and climatic changes on phytoplankton bloom events. In this context, motivated by the importance of understanding the environmental mechanisms assigned to phytoplankton bloom events and considering the difficulties imposed by field data collection, our study focuses on analyzing the mentioned issue only using remotely sensed time series data. For this purpose, we performed a temporal analysis between 1985 and 2018 over a portion of the Barra Bonita Hydroelectric Reservoir, Brazil. Initially, we obtained the landscape occupation, precipitation, and temperature information from the MapBiomas, FLDAS, and CHIRPS projects, respectively. A fully automatic algorithm fed by Landsat image series and supported by Google Earth Engine functions was developed and employed to identify and quantify phytoplankton bloom events. Then, the obtained data were inspected by distinct statistical procedures, including correlation and trend analysis. Although there was an absence of a relationship between the climatic components and the emergence of phytoplankton blooms, it was identified using linear regression models (R2 ≥ 78 % ) an intensification of blooms after the increase in nonnatural forestry areas, reduction of pastures, and advance of agricultural areas. Furthermore, machine learning methods were employed to obtain nonlinear regression models (R2 ≥ 73 % ), making evident that the landscape changes are mainly responsible for the phytoplankton insurgences in the analyzed region. This result agrees with other studies found in the literature and highlights the possibility of investigating anthropogenic eutrophication only using remotely sensed data and automatic algorithms.

Qualitative and quantitative study of algae in three drinking water plants supply springs in Sulaymaniyah province - Kurdistan region of Iraq

In this study, three drinking water treatment plant supply springs were selected within different sites in Sulaymaniyah province- Kurdistan region of Iraq. Samples were collected over period of eight months from May to the end of December 2015.
 Five stations were selected, Stations 1, 2 and 3 were located at Bestan Sowr drinking water project in Sharazur district, station 4 was located at Saray Subhan Agha drinking water project in Said sadiq district and station 5 was located at Khurmal drinking water project in Khurmal district within Halabja district.
 The study involved a qualitative (identification) and quantitative (Density and Total count) study of phytoplankton in water for selected stations.
 A total of 155 algal species were identified belong to 9 classes in all studied stations, 80 species belonged to Bacillariophyceae (diatoms), 35 species to chlorophyceae, 30 species to Cyanophyceae, 3 species to Euglenophyceae, 2 species for each of Crptophyceae and Pyrophyceae and 1 species for each of Chrysophyceae, Dinophyceae and Xanthophyceae. Diatoms were dominated (according to the total count of taxa) over all other phytoplankton in all sites, Chlorophyceae formed the second most algal group at the selected sites and Cyanophyceae formed the third most algal group of phytoplankton at the selected sites.
 The results of phytoplankton quantitative study in the studying stations recorded the highest total density of phytoplankton during the study period was at Station1 (18377.28 ind×103/l), followed by (12513.34 ind×103/l) at Station 2 and (4779.45 ind×103/l) at Station 3. The results of total Count of phytoplankton at all stations ranged between 5913×103 cell/l and 29×103 cell/l.

Effects of Land Use and Physicochemical Factors on Phytoplankton Community Structure: The Case of Two Fluvial Lakes in the Lower Reach of the Yangtze River, China

Potential changes in phytoplankton community structure in shallow lakes due to land use could pose a serious threat to ecosystem sustainability and functioning. Nevertheless, this effect has not been analyzed in detail. In this study, we chose two adjacent lakes, the main land use types around them are farmland and forest, respectively. We investigated the spatial differences in the phytoplankton community structure, water quality physicochemical parameters, and land use patterns in the two lakes. The results indicated that the annual average cell density and biomass of phytoplankton in the former were 1.84 times and 2.38 times that of the latter, respectively. The results of Pearson correlation and Redundancy analysis showed that total nitrogen (TN), total phosphorus (TP), water depth (WD), and water temperature (WT) were the main environmental factors influencing the structural changes of phytoplankton communities in the two lakes. The results indicated that different land use patterns, such as farmland and towns around the lake, increase the nitrogen (N) and phosphorus (P) content of the lake, while the forests distributed around the lake can reduce the N and P entering the lake, which is probably the main reason for the spatial difference in the characteristics of phytoplankton communities in the two lakes. Our results highlight that land use significantly affects the community structure of phytoplankton by influencing physicochemical factors in water bodies. Our study can provide guidance for pollution control and water quality management of shallow lakes.

Phytoplankton and benthic infauna responses to aeration, an experimental ecological remediation, in a polluted subtropical estuary with organic-rich sediments.

Fine-grained organic-rich sediments (FGORS) are accumulating in estuaries worldwide, with multi-faceted negative ecosystem impacts. A pilot experiment was carried out in a residential canal of the Indian River Lagoon estuary (IRL, Florida, USA) using an aeration treatment intended to mitigate the harmful ecological effects of organic-rich sediment pollution. Planktonic and benthic communities were monitored, and environmental data collected throughout the aeration process. Results were compared against control conditions to evaluate the efficacy of aeration in the mitigation of FGORS. During the aeration process, hurricane Irma impacted the study area, bringing heavy rainfall and spawning a brown tide event (Aureoumbra lagunensis). The overall thickness and volume of FGORS, and the organic content of surface sediments did not change during the aeration treatment. Dissolved oxygen was higher and ammonium concentrations were lower in aeration canal bottom water compared to the control canal. During treatment, aeration did facilitate benthic animal life when temperatures dropped below 25°C, likely due to water column mixing and the increased capacity of water to hold dissolved gasses. In general, aeration did not significantly change the planktonic community composition relative to the control canal, but, during the post-bloom period, aeration helped to weaken the brown tide and phytoplankton densities were 35-50% lower for A. lagunensis in aeration canal surface water compared to the control canal. Aeration has important management applications and may be useful for mitigating algal blooms in flow-restricted areas and promoting benthic communities in cooler environments.

Effects of submerged macrophytes (Elodea nuttallii) on water quality and microbial communities of largemouth bass (Micropterus salmoides) ponds.

Traditional aquaculture ponds are one of the most vulnerable ecosystems; thus, ecological aquaculture is increasingly valued for its beneficial ecological properties and ecosystem services. However, little is known about ecological aquaculture of largemouth bass with submerged vegetation. Here, we designed three ecological ponds of cultured largemouth bass with submerged macrophytes (the EM group) and three ponds with traditional aquaculture (the M group) to reveal the response of water quality, and phytoplankton and bacterial communities, to submerged macrophyte bioremediation during a 90-day culture period. We observed that Cyanobacterial outbreak occurred in the M group ponds from day 7 to the end of the experiment; however, there were no Cyanobacterial blooms in the EM group ponds throughout the culture period. Compared with the M group ponds, the EM group ponds, which had submerged hydrophytes, had significantly decreased concentrations of TP, TN, and CODMn, but significantly increased DO concentrations throughout the experimental period. Moreover, ecological aquaculture with submerged macrophytes showed strong effects on the phytoplankton and bacterial community compositions. In particular, the M group ponds had higher phytoplankton density and mainly included Cyanobacteria, whereas the EM group had lower phytoplankton density and mainly included Chlorophyta. Moreover, higher alpha diversity, as determined by Ace and Simpson index values, was detected for bacterial communities in the EM group ponds. Furthermore, PCoA clearly grouped the bacterial communities according to the two culture modes throughout the culture period. These results indicate that ecological aquaculture with submerged macrophytes can improve water quality, control Cyanobacterial blooms, and affect the diversity and composition of bacterial communities. These valuable effects seem to be beneficial and consistent to maintaining aquaculture ecosystem stability.

Effects of Water Stratification and Mixing on Plankton Community Structure in a Floating Solar Power Plant

Plankton community structure play pivotal roles in aquatic ecosystems, influencing their structure, function and services. However, little is known about the effects of water stratification and mixing on the dynamics of aquatic ecosystems. The influence of water stratification and mixing on plankton community structure was studied in the Floating Da Mi Solar Power Plant was done between March 2020 and September 2022, encompassing both dry and rainy seasons. Data from 4 sites were used as a representative example for the study area to conduct a qualitative study. To implement this assessment, the analyses were based on MRC methods and classifications, these improved by the scientific group. The results showed that 86 species of phytoplankton and 23 species of zooplankton were found in the study area. The density of phytoplankton at each site ranged from 279 to 32,282 individuals/sample, while the density of zooplankton at each site fluctuated from 5 to 33 individuals/sample. The calculated values for the diversity index (H’) of phytoplankton and zooplankton fluctuated from medium to quite high levels from 1.55 to 3.69; 1.562.95 respectively. The results also showed that several environmental variables, including temperature, dissolved oxygen, and chlorophyll-a were correlated with species richness, density and diversity index of phytoplankton and zooplankton. The obtained results will be useful for the monitoring of changes of aquatic ecosystem at the study area, in particular the sensitivity of aquatic flora and fauna to changes in environmental variables.

State of marine biota in the water area of the Muchke Bay’s Coal Terminal of the Tatar Strait

An analysis of the species composition of phytoplankton and ichthyoplankton was carried out for the first time in the port water area of the Muchke Bay (Tatar Strait) in autumn. The species composition, distribution features and structure of macrozoobenthos were considered. Phytoplankton density is evenly distributed in the study area. The density of diatoms reached 97 % of the total phytoplankton density, and the biomass was 99 %. The microalgae Sceletonema costatum (Greville) Cleve, 1873 and Cylindrotheca closterium (Ehrenberg) Reimann & J.C.Lewin, 1964, species that live in polluted waters, were discovered. The development of phytoplankton in the autumn period was active, but the peak of flowering was not observed. Ichthyoplankton in October 2017 is represented by live eggs of Limanda sakhalinensis (Schmidt, 1904) (8 ind./m3), in September 2018 - by the larvae of Hexagrammos stelleri Tilesius, 1810 (0.003-0.056 ind./m3) and H. octogrammus (Pallas, 1814) (0.01-0.077 ind./m3). Up to 85 representatives of macrozoobenthos were registered from the research area, including 40 species of Polychaeta, 19 ones of Crustacea, 16 species of Mollusca, 5 ones of Echinodermata and 5 species of other fauna groups. After dredging, a decrease in the species diversity of phytoplankton, ichthyoplankton and macrozoobenthos was found in the samples.

Spatial and Temporal Variations of Dissolved Inorganic Nutrients and Relationship with Phytoplankton Density in Coastal Water of Kudat, Sabah, Malaysia

Spatial and Temporal Variations of Dissolved Inorganic Nutrients and Relationship with Phytoplankton Density in Coastal Water of Kudat, Sabah, Malaysia

Seasonal variation of zooplankton assemblages and their responses to water chemistry and microcystin content in shallow lakes in Thailand

This study examines zooplankton assemblage structure and density from five hypereutrophic urban shallow lakes between cool and hot periods in 2018-2019. We analyzed the variation of zooplankton and their relationship with environmental factors. Samples of zooplankton were collected from shallow lakes in different regions of Thailand. Four groups of zooplankton were identified, of which Rotifera was the most abundant group, followed by Copepoda, Protozoa, and Cladocera. Zooplankton assemblages were influenced by seasons, as indicated by multidimensional scaling analysis. The number of species and density of zooplankton were lower during the cool period than during the hot period. The increased density of zooplankton in the hot period may have been due to increased phytoplankton density as food sources. Pearson?s correlation coefficient revealed that Rotifera and Copepoda positively correlated with the temperature and pH, and Rotifera was negatively correlated with total phosphorus; a negative correlation was also observed between Protozoa and dissolved oxygen. The microcystin content tended to have a negative impact on specific small species such as Protozoa (Coleps sp.). Information from this research is important for further study involving factors affecting the size structure of zooplankton communities, especially large-bodied species in tropical regions.

Stability switch and Hopf bifurcations for a diffusive plankton system with nonlocal competition and toxic effect

<abstract><p>Since the distribution of plankton is always uneven, the nonlocal phytoplankton competition term indicates the spatial weighted mean of phytoplankton density, which is introduced into the plankton model with toxic substances effect to study the corresponding dynamic behavior. The stability of the positive equilibrium point and the existence of Hopf bifurcations are discussed by analysing the distribution of eigenvalues. The direction and stability of bifurcation periodic solution are researched based on an extended central manifold method and normal theory. Finally, spatially inhomogeneous oscillations are observed in the vicinity of the Hopf bifurcations. Through numerical simulation, we can observe that the system without nonlocal competition term only generates homogeneous periodic solution, and inhomogeneous periodic solution will produce only when both diffusion and nonlocal competition exist simultaneously. We can also see that when the toxin-producing rate of each phytoplankton is in an appropriate range, the system with nonlocal competition generates a stability switch with inhomogeneous periodic solution, when the value of time delay is in a certain interval, then Hopf bifurcations will appear, and with the increase of time delay, the quantity of plankton will eventually become stable.</p></abstract>

From diatoms to killer whales: impacts of pink salmon on North Pacific ecosystems

In response to a climate regime shift in 1977 and general heating of the North Pacific Ocean, pink salmon Oncorhynchus gorbuscha abundance reached record highs during 2005-2021, comprising 70% of all Pacific salmon. Pink salmon are approximately 25 times more numerous in odd- than even-numbered calendar years in some major North Pacific ecosystems, a unique demographic pattern analogous to repeating whole ecosystem treatment-control experiments. We found compelling examples indicating that in odd years, predation by pink salmon can initiate pelagic trophic cascades by reducing herbivorous zooplankton abundance sufficiently that phytoplankton densities increase, with opposite patterns in even years. Widespread interspecific competition for common-pool prey resources can be dominated by pink salmon, as indicated by numerous biennial patterns in the diet, growth, survival, abundance, age-at-maturation, distribution, and/or phenology of ecologically, culturally, and economically important forage fishes, squid, Pacific salmon and steelhead trout Oncorhynchus spp., seabirds, humpback whales Megaptera novaeangliae, and endangered southern resident killer whales Orcinus orca. In aggregate, the evidence indicates that open-ocean marine carrying capacity in the northern North Pacific Ocean and Bering Sea can be mediated by top-down forcing by pink salmon and by ocean heating, and that large-scale hatchery production (~40% of the total adult and immature salmon biomass) likely has unintended consequences for wild salmon, including Chinook salmon O. tshawytscha, and many other marine species. Further investigation of the effects of pink salmon on other species will increase our knowledge of ecosystem function and the important role top-down forcing plays in the open ocean

Ecological Insights from Phytoplankton Diversity Off Veraval, Gujarat Coast, India

Phytoplankton species are sensitive to environmental and seasonal variability. This property of phytoplankton can be used to predict and study fluctuations in the ecological health of the system. In this study, phytoplankton diversity and its direct interactions with abiotic components of the ecosystem were studied to evaluate the health and stability of the coastal waters of Veraval, Gujarat coast, India. Results showed that diatoms dominated the ecosystem with a strong seasonal pattern of community succession. Waters were well churned and turbidity hindered penetration of light into deeper layers during the fall and winter monsoon season whereas stratification during spring inter-monsoon governed the distribution of different phytoplankton groups in the water column. These seasonal shifts resulted in a sincere pattern of annually re-occurring seasonal succession and formation of bloom events in the region. Apart from general phytoplankton diversity and its seasonal succession, the study intended to understand the forces governing the diversity and ecological system as a whole. To meet this objective, percent light intensities of chlorophyll-a, at various depths and temperatures were studied in relation to phytoplankton density. The correlation did not stand well for stations having active bloom formation showing that chlorophyll-a cannot be used as a proxy of phytoplankton biomass during bloom conditions. Thus excluding the points corresponding to active bloom conditions, second order polynomial equations were developed explaining the changes in chlorophyll-a concentration with variations in phytoplankton cell counts for study seasons. It was observed that most phytoplankton cells preferred upper well-lit layers of the water column with 100% light intensity followed by depths with 50% and 1% light intensities respectively. Study on temporal dynamics of the phytoplankton community in relation to temperature showed that the winter monsoon was characterized by a temperature range of 21.9 °C to 29 °C where Navicula distans was the most abundant phytoplankton species. Skeletonema costatum was the most abundant species at 27.2 °C during fall intermonsoon. Spring inter monsoon had an abundance of Navicula distans at both 28.35 °C and 28.9 °C.

Algal population growth and dynamics of Asan Wetland

A one year study of the phytoplankton community composition was carried out in the Asan wetland, a reservoir fed by River Yamuna in Uttarakhand India. In terms of bio-volume, phytoplankton community was generally dominated by Bacillariophyceae. Mean phytoplankton standing crops were highest in the wetland. The frequency and severity of algal blooms was increased significantly. To control their expansion, it was essential to identify the factors responsible for blooming of waters. Nutrient enrichment (mainly due to anthropogenic activities) and environmental factors (including the climate change) were considered the major catalyst for onset, proliferation and development of blooms. The phytoplankton of the Asan wetland was studied for one year with physical and chemical variables in relation to a pollution gradient. Analysis of the physical and chemical variables and phytoplankton density indicated that the wetland is experiencing heavy pressure of pollution due to anthropogenic activities. The dominant phytoplankton community mainly comprises of family, Chlorophyceae, Bacillariophyceae and Myxophyceae. Physical factors, though vital, had an indirect effect in facilitating the interaction among various available nutrients. In terms of phytoplankton density and diversity common genera observed include Chlorella, Chlaymydomonas, Spirogyra, Ulothrix, Hydrodictyon, Cladophora, Cosmarium, Chlorococcum, Oedogonium, Microspora, Desmidium, Chara, Zygenema, Syndesmus, Volvox, Ceratoneis, Amphora, Caloneis, Fragilaria, Navicula, Synedra, Diatoms, Gomphonema, Pinnularia, Melosira, Tabellaria, Denticula, Cymbella, Cyclotella, Nostoc, Anabaena, Oscillatoria, Rivularia, Coccochloris and Phormidium. Several genera were found most prominent during the study period having no seasonal impact on their abundance and variation. The spatial and temporal patterns observed in some of these dominant species were attributable to patterns in key environmental variables including temperature, flow, pH, dissolved oxygen and nutrient concentrations.

Đa dạng sinh học thực vật phù du ở vùng hạ lưu sông Vàm Cỏ, tỉnh Long An

The study was conducted at ten sites in the lower of Vam Co river, Long An province from January to July 2018. The samples were collected by phytoplankton net and fixed with 5% formalin at the field. A total of 223 phytoplankton species were recorded, belonging to 106 genera, 66 families, 37 orders, and 6 divisions, of which the diatom group dominated in the species number. The average cell density ranged from 27 144 ± 8 508 cells/liter to 153 743 ± 45 300 cells/liter. The dominant species recorded in the study area include Merismopedia punctata, Oscillatoria acuta, Oscillatoria perornata, Oscillatoria sp., Microcystis aeruginosa, Microcystis panniformis, Lyngbya martensiana, Cyclotella meneghiniana, Skeletonema costatum, Coscinodiscus jonesianus, Melosira granulata. The high densities of phytoplankton were rich food sources for larvae, zooplankton, shrimp, fish, and bivalves. The Shannon - Weiner index, Simpson index, and Margalef index showed that the phytoplankton of lower Long An was diverse and abundant.

Autoecology of Ceratium furca and Chaetoceros didymus as potential harmful algal blooms in tourism and aquaculture sites at Teluk Pandan Bay, Lampung, Indonesia

Abstract. Hasani Q, Yusup MW, Caesario R, Julian D, Muhtadi A. 2022. Autoecology of Ceratium furca and Chaetoceros didymus as potential harmful algal blooms in tourism and aquaculture sites at Teluk Pandan Bay, Lampung, Indonesia. Biodiversitas 23: 5670-5680. Harmful algal blooms (HABs) phenomenon has been observed around tourism and aquaculture sites in Teluk Pandan Waters, Lampung Bay. The dominant potential HABs found in Teluk Pandan waters were Ceratium furca and Chaetoceros didymus. This study aimed to analyze the relationship between the environmental physicochemical factors and the abundance of C. furca and C. didymus as potential HABs. Phytoplankton samples were collected from four stations (Hurun Bay, Sidodadi Coastal Waters, Sari Ringgung Beach and Cikunyinyi Bay) during May-August 2022. Physical parameters (temperature, depth, brightness, current velocity and salinity), as well as chemical parameters (dissolved oxygen, pH, phosphate, nitrite, nitrate and ammonia) were all measured in conjunction with phytoplankton sampling. Canonical correlation analysis and multiple regression were used to predict the effect of environmental parameters on phytoplankton density. Blooms of C. furca were found with the highest density at 5.417×106 cells/L in Cikunyiyi Bay, while C. didymus predominated in Hurun Bay (2.890×104 cells/L), Sidodadi Coastal Waters (3.923×104 cells/L) and Sari Ringgung Beach (3.531×104 cells/L). The main factors influencing the increase in C. furca population at Cikunyinyi Bay were pH, phosphate and nitrate. The increase in C. didymus population at Sidodadi Coastal Waters was affected by phosphate, nitrate and nitrite, while phosphate and nitrate influenced the increase in C. didymus population at Sari Ringgung Beach. Potentially HABs density was found to be higher near intensive shrimp farming sites. The use of fertilizer and artificial feed in high quantities is thought to be responsible for increased water eutrophication. Periodic monitoring and consistent determination of environmental carrying capacity for intensive shrimp farming activities are required to control HABs and ensure the sustainability of aquaculture and tourism activities in Teluk Pandan Waters.

COVID-19 Lockdowns Promoted Recovery of the Yangtze River’s Aquatic Ecosystem

The impacts of COVID-19 lockdowns on human life, air quality, and river water quality around the world have received significant attention. In comparison, assessments of the implications for freshwater ecosystems are relatively rare. This study explored the impact of COVID-19 lockdowns on aquatic ecosystems in the Yangtze River by comparing river water quality, phytoplankton, zooplankton, and fish data collected at the site in the middle reach of the Yangtze River in 2018 and 2020. The results show that during COVID-19 lockdowns, the reduction in industrial and domestic effluent discharge led to a reduction in organic pollution and industrial plant nutrient pollution in rivers. Among them, PO43−−P, CODMn, and TP were significantly decreased (p < 0.05). During lockdowns, nutrient supplies such as TN and TP were reduced, which led to inhibition of algae growth and decreased phytoplankton abundance. Phytoplankton affects the abundance of zooplankton through a bottom-up effect, and a decrease in phytoplankton density leads to a decrease in zooplankton density. The decrease in plankton density led to lower primary productivity in rivers, reduced fish feed supplies, intensified competition among fish populations, with increases in population dominated by high trophic level carnivorous fish. In addition, the decrease in fishing intensity has contributed to an increase in the number of rivers–sea migratory fish; the fish community was earlier mainly dominated by small-sized species with a short life cycle, and the number of supplementary populations has now increased. As a consequence, the fish community structure shows a tendency toward high complexity and high fish diversity. Overall, these observations demonstrate that the rapid revival of the retrogressive Yangtze River ecosystem is possible through limitation of anthropic interferences.

Acoustic disturbance in blue mussels: sound-induced valve closure varies with pulse train speed but does not affect phytoplankton clearance rate

Abstract Anthropogenic sound has increasingly become part of the marine soundscape and may negatively affect animals across all taxa. Invertebrates, including bivalves, received limited attention even though they make up a significant part of the marine biomass and are very important for higher trophic levels. Behavioural studies are critical to evaluate individual and potentially population-level impacts of noise and can be used to compare the effects of different sounds. In the current study, we examined the effect of impulsive sounds with different pulse rates on the valve gape behaviour and phytoplankton clearance rate of blue mussels (Mytilus spp.). We monitored the mussels’ valve gape using an electromagnetic valve gape monitor and their clearance rate using spectrophotometry of phytoplankton densities in the water. We found that the mussels’ valve gape was positively correlated with their clearance rate, but the sound exposure did not significantly affect the clearance rate or reduce the valve gape of the mussels. They did close their valves upon the onset of a pulse train, but the majority of the individuals recovered to pre-exposure valve gape levels during the exposure. Individuals that were exposed to faster pulse trains returned to their baseline valve gape faster. Our results show that different sound exposures can affect animals differently, which should be taken into account for noise pollution impact assessments and mitigation measures.

Diversity of Coastal Phytoplankton in Balayan Bay, Batangas, Philippines

Phytoplankton composition, density, and their relation with 10 abiotic water parameters in six coastal stations [four marine (Anilao, San Luis, Calatagan, and Balayan) and two freshwater (Palanas and Pansipit)] in Balayan Bay, Batangas, Philippines were examined monthly for one year (February 2006–January 2007). A total of 97 taxa of phytoplankton in four phyla were observed. About 85% of these taxa were diatoms (Bacillariophyta). The mean monthly density of phytoplankton ranged from 2,367 (Pansipit Station) to 2,992 units · mL–1 (San Luis Station), with as much as 93% of the total phytoplankton density being made up of diatoms. Cyclotella meneghiniana, a centric diatom, had the highest mean monthly density (143 units · mL–1) in all the stations. Among the six stations, the marine stations generally showed higher phytoplankton density (maximum monthly value = 4,700 units · mL–1, Anilao, in January), species diversity index (maximum monthly value, H’ = 1.402, Balayan, in March), and species richness (maximum monthly value, 29, Balayan, in March) than the freshwater stations. Clear differences were also detected in the physico-chemical characteristics between the freshwater and marine stations. Among the 10 abiotic parameters monitored, mean monthly salinity ranged from 0.92–1.02 psu in freshwater stations and 29.1–32.6 psu in marine stations. Mean monthly water temperatures ranged from 23–33.5 °C and pH ranged from 7.87–8.23. Conductivity in the two freshwater stations ranged from 2,006.17–2,051.92 μS · cm–1 and was 45x of that of the marine stations, which ranged from 44.57–50.48 μS · cm–1. Generally, marine stations showed higher values of total solids, total dissolved solids, and total suspended solids than the freshwater stations. However, marine stations recorded greater water clarity than the freshwater stations (mean monthly depth of Secchi disc ranged from 1.68–3.65 m). Freshwater stations recorded higher mean monthly orthophosphate-P values but generally lower nitrate-N values than the marine stations. These values (1.65–4.31 ppm PO4-P or 0.29–1.41 ppm P; 2.58–5.35 ppm NO3-N or 0.428–1.509 ppm N) are within or near the Philippine standard value of 1.0 ppm for P and N for clean marine water. Changes in some of these abiotic parameters were correlated with changes in the population density of some of the dominant species, to total mean monthly phytoplankton density, species diversity index, and species richness in some of the stations, but no single parameter can explain the biological patterns observed for all stations. No algal bloom was observed during the course of this study, although a potentially harmful dinoflagellate, Ceratium furca, was observed. It was never a dominant alga in any of the stations.

Impact of some physico-chemical factors distribution on the density of phytoplankton in the Shafya River / Iraq

The study dealt with phytoplankton in the Shafya River, where water and phytoplankton samples were collected monthly from three selected sites starting from December 2021 until May 2022, where physical and chemical factors were studied in addition to the composition of the phytoplankton community in those sites .The results showed the diagnosis of 147 taxonomic ranks of phytoplankton, Bacillariophyceae were absolutely dominant in all locations and months with 81 taxonomic ranks, followed by Chlorophyceae, 32 taxonomic ranks, 26 taxonomic ranks to cyanophyceae, 6 ranks to euglenophyceae, and one rank each to Dinophyceae and Crysophyta golden. In this study, some vital evidence such as the Shannon-Weiner Guide, the Jacquard Guide and the Wealth Guide, it was shown through the results that Shannon's values at sites and most months decreased to less than 1 indicating that the water of the Shafya River is contaminated.

Phytoplankton Community in Relation to Environmental Variables in the Tidal Mangrove Creeks of the Pasur River Estuary, Bangladesh

The Pasur River estuary (PRE) provides vital fishery resources and supports millions of livelihoods in the southwestern coastal region of Bangladesh. Our research focused on phytoplankton community assemblages, alpha diversity indices, and the seasonal succession of major phytoplankton species in relation to physicochemical parameters in the tidal mangrove creeks of the Pasur River estuary. Spatial and temporal variations were assessed by water sampling at 17 stations in the study area from January to December 2019. The mean salinity level in the tidal mangrove creeks of the PRE was significantly (p < 0.05) higher during the dry season than during the wet season. Spatially, no significant variation (p > 0.05) was observed in the dissolved inorganic nitrogen and dissolved inorganic phosphorus between PRE and mangrove creeks, but temporally, the variables varied significantly (p < 0.05). Spatially, no significant variation (p > 0.05) was observed in the alpha diversity of the phytoplankton community but significantly (p < 0.05) varied temporally. Blue-green algae became dominant in the oligohaline conditions during the wet season, while diatoms were dominant during the dry season which severely depleted dissolved silica. In terms of phytoplankton species diversity, our study classifies the study areas as highly diversified zones. Phytoplankton succession from diatoms (dry season) to blue-green algae (wet season) is attributed to the changes in the physicochemical and nutrient parameters depending on seasonal environmental parameter fluctuations. This study illustrated that phytoplankton diversity and density varied with the degrees of habitat and seasonal changes, implying the potential impacts of anthropogenic activities and natural causes on their community structure in tropical estuaries and mangrove creeks.